1. Field of the Invention
The present invention is related to a method of determining the driving currents of a backlight module, and more particularly, to a method of determining the driving currents of a plurality of areas of the backlight module for circulating the temperature of the backlight module evenly.
2. Description of the Prior Art
LCD (Liquid Crystal Display) devices have gradually become the main stream display device due to the advantages of high display quality, radiation-free, and high spatial efficiency. The liquid crystal itself does not emit light, so the LCD device requires a backlight module for providing the light source required by the liquid crystal panel to display images.
The conventional backlight module comprises the light emitting component and the corresponding driver, wherein the driver comprises components such as the power transistor and the transformer. Heat of the backlight is generated when the driver is operating. In addition, the light emitting component also generates heat when emitting light. Consequently, such heat sources cause the temperature of the backlight module to rise. A gap exists between the light emitting component of the backlight module and the crystal panel for the purpose of light blending. The heat generated within the backlight module causes air convection between the gap. When the air of the lower part of the backlight module is heated due to the heat generated from the light emitting component and the driver, the air convection causes the hot air to flow upwards as the hot air consists of a lower density. As the upper part of the lamp holder is structurally sealed, heat is gradually accumulated as the hot air flows upwards, resulting in temperature difference between the upper part and the lower part of the internal of the backlight module. The accumulated heat affects the heat dissipating ability of the light emitting component and the driver of the backlight module, further influencing the light emitting efficiency of the backlight module.
Please refer to FIG. 1. FIG. 1 is a diagram illustrating the approximate temperature measurement of different areas of the LCD device according to the prior art. The LCD device 100 comprises a backlight module 110 and a base 120. Taking the vertical-structured LEDs (Light Emitting Diodes) as an example, the LEDs are distributed at the lower portion of the light emitting surface of the backlight module 110, the LCD device 100 is normally used perpendicular to the ground surface and the backlight module 110 is installed on the base 120. When the backlight module 110 is disposed vertically, the temperature of the LEDs of different areas of the backlight module 110 is varied such that the maximum temperature difference can reach up to tens of degrees Celsius (° C.). The temperature difference severely affects the lifetime of the LEDs of different areas of the backlight module 110, and generally the operating current of the LED is constrained by the maximum temperature of each area of the backlight module 110. The temperature difference between the lamp holders of different areas causes the optical film to inflate, as a result the optical film may become wavy and the display quality is degraded. Furthermore, after a period of usage, the brightness uniformity of the backlight module 110 is significantly varied as the LEDs of different areas are attenuated at different rates, consequently the display quality of the backlight module 110 is deteriorated severely.